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Printing Units Troubleshooting - Doubling

Definition:  Doubling, not to be confused with slurring, is caused by improper transfer of image from the blanket to the paper.  After the plate transfers ink to the blanket, it should then ideally all transfer to the paper.  If it does not, then the blanket revolves around to pick up the same dot, but on a slightly different position on the blanket.  The blanket then transfers a "double image" to the paper.


Problem:  Too much packing under the blanket.
Solution:  Check that you are the proper height over bearer on your blanket.  Essentially what is happening is that the blanket cylinder is travelling slightly faster than the plate.  A slight sliding action occurs and produces a double image.  Reduce the packing if necessary.


Problem:  Improper bearer pressure.
Solution:  Follow the procedure for checking and setting your bearer pressure properly.


Problem:  Worn gears or bearings.
Solution:  If your press is old, you need to consider this possibility.  Play in the gears can cause slight "bumps" while running.  Additionally, the main cylinder bearings that are wearing will cause slight hesitations or even pressure variations between the cylinders.  Have a mechanic thoroughly check these parts.


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